I find myself frequently presented with what I will call "meta-puzzle" logical choices, and I am wondering if any of you have an opinion on it.

As an example, take a typical Hitori puzzle. Imagine that a certain square has the number "5" in it. I examine the row and the column containing that "5" and notice there are no other 5's in the same row or column. I know that the "5" cannot be 'forced' to be shaded unless there is another "5" in the same row or column. I also know this puzzle must have a single unique solution. Thus, the "5" must be unshaded.

This logic bothers me, however, because it assumes the puzzle has a unique solution. As such I try to avoid marking the "5" as unshaded until the puzzle 'forces' me to (by blocking an unshaded group in to a corner, for example). Though, to be honest, most such squares that do come up do not have a large effect on the overall outcome anyway.

Regardless, I am interested in the opinions of others on this point. Do you think that assuming the puzzle has a single, unique solution is a valid logical step, or do you prefer working under the assumption that the puzzle might have more than one solution and "discovering" that it, in fact, only has one solution after all?

When I started with Hitoris, I used the property you described. However when I came more skilled I started to have the same doubts you have.

Nowadays I stick to the original rules even though I know that I can trust the validity of Conceptis puzzles. During all the 7 years I have solved their puzzles only one nonvalid puzzle has appeared and it was just a human error.

I think for all the best way is the way they enjoy. I admit cheating sometimes with puzzles I don't master very well. Skill comes by experience, and after solving more and more you can finally "see" how the puzzle really works.